Solid state light amplifying device with sintered photoconductor and electro-luminescent input panel



p 21, 1965 MITSURU OIKAWA 7, 6

SOLID STATE LIGHT AMPLIFYING DEVICE WITH SINTERED PHOTOCONDUCTOR AND ELECTROLUMINESGENT INPUT PANEL Filed April 5, 1961 United States Patent 3,207,906 SOLID STATE LIGHT AMPLIFYING DEVICE WITH SINTERED PHOTOCONDUCTOR AND ELECTRO- LUMINESCENT INPUT PANEL Mitsuru Oikawa, Tokyo-to, Japan, assignor to Kabushiki Kaisha Hitachi Seisakusho, Tokyo-t0, Japan, a jointstock company of Japan Filed Apr. 3, 1961, Ser. No. 100,343 Claims priority, application .lapan, Apr. 6, 1960, 35/ 20,275 4 Claims. (Cl. 250213) This invention relates to a new and improved electroluminescent indicating apparatus whereby excellent pictures can be obtained.

The nature, objects, and details of the invention will become clearly apparent by reference to the following detailed description when taken in connection with the accompanying drawing in which the same and equivalent parts are designated by the same reference numerals or letters, and in which:

FIGURE 1 is a diagrammatic, perspective view showing the construction of an ordinary electroluminescent (hereinafter referred to by the abbreviation EL) indicating apparatus of known kind;

FIGURE 2 is a perspective view showing a portion of the construction of an output EL apparatus for observation to be used in the present invention;

FIGURE 3 is a diagrammatic perspective view showing an example embodiment of the EL indicating apparatus of the present invention; and

FIGURE 4 is a graphical representation for description of the operation of the embodiment shown in FIG. 3.

EL indicating apparatuses of the type wherein mutual intersecting electrodes are arranged on opposite surfaces of an electroluminescent layer, and a scanning voltage is impressed across the two electrodes to cause an intersecting point at any position to luminesce and thereby indicate position have been proposed. One example construction thereof is shown in FIG. 1, wherein an EL layer E has on one surface thereof a group of electrodes x x x and on the opposite surface thereof another group of electrodes y y y,,, the electrodes of the two said groups extending in substantially perpendicular directions to form intersections.

An indicating apparatus of the above-mentioned kind has a disadvantage in that, since the EL layer E used can luminesce only during the impressing of voltage, and there is almost no afterglow effect, the output optical image of the intersections cannot be recognized sufliciently when the voltage signal scanning is rapid.

While, in an endeavour to reduce this disadvantage, improvement of the characteristics of the EL substance itself has been considered and studied, a satisfactory solution of the problem has not yet been proposed.

It is an essential object of the present invention to provide a new and improved EL indicating apparatus capable of producing excellent pictures.

Said object, other objects, and advantages of the invention have been attained by combining, additionally, an output EL indicating apparatus for observation with the above-described EL indicating apparatus.

The output EL indicating apparatus for observation necessary for the present invention is according to the following description. This output EL indicating apparatus for observation receives an instantaneous luminescence at any position of the input EL apparatus, causes a delayed luminescence to be generated in the EL layer at a position corresponding to the osition of the aforesaid instantaneous luminescence, and accomplishes indication by means of the luminescing position of the said delayed luminescence. The principal structure of this "ice apparatus comprises a photoconductive layer, which has delayed resistance drop characteristic due to illumination, and an EL layer, and is the same as the so-called solidlight amplifying plate. It differs from such -a plate used merely as a light amplifying plate in that, in the present case, together with its light amplifying effect, the delayed resistance dro characteristic of the photoconductive material is utilized. Moreover, since the said apparatus is to amplify EL, it is necessary that it be of high sensitivity.

One example of a practical embodiment of such an output EL apparatus for observation to be used for the EL indicating apparatus of the present invention is illustrated in FIG. 2. As shown, the principal structure comprises a transparent electrode 2 of flat plate form sandwiched between a glass plate 1 and an EL layer E On the EL layer, split electrodes 3 are attached in rows. Heat-resistant, insulating posts 4 are attached adhesively along each row of the said electrodes 3. A wire electrode 5 and a photoconductive layer 6 are formed on the upper surfaces of the said posts 4 in the axial direction (direction of the row). On the side faces of the said posts 4, auxiliary split electrodes 3a are formed so as to be aligned with the aforesaid split electrodes 3 and, at the same time, to clamp the photoconductive layer 6 between themselves and the Wire electrode 5.

The heat-resistant, insulating posts are made of such a material as a ceramic bar. The cross section of these posts may be of any shape, such as \a rectangle or a semicircle, to suit the requirements. When the photoconductive layer 6 is to be formed on a surface of these posts 4, this is accomplished byplacing a suitable masking body thereon and applying thereon a coating of a pulverized photoconductive substance, such as CdS, in paste state, then sintering the said coating by placing the posts with coating in a furnace at a temperature of the order of 600 degrees C. Then the wire electrode 5 and the auxiliary split electrodes 3a are made to adhere on both sides in the axial direction by such an expedient as spraying with silver paint, after which the bottom of the assembly is made to adhere on the row of the split electrodes 3 by means of such a substance as Araldis resin. Several of these heat-resistant, insulating posts assembled, in the above-described manner, with a sintered photoconductive layer, wire electrode, and auxiliary split electrodes are made and attached on all rows of split electrodes 3. Finally, electrical contact between the auxiliary split electrodes 3a of the heat-resistant, insulating post surface and their respectively corresponding split electrodes 3 is established by such means as silver paint.

When, with the apparatus thus constructed, an electric power source is connected between the Wire electrode 5 on the heat-resistant, insulating posts 4 and the flat-plate electrode 2, a voltage is impressed on the EL layer E by way of the sintered photoconductive layer 6, auxiliary split electrodes 3a, and the split electrodes 3, and each portion luminesces in accordance with the magnitude of resistance (varying with illumination) of the photoconductive layer 6.

The conventional photoconductive layers known heretofore have been made, in general, by scattering particles of such substances as CdS in a synthetic resin and forming the layer in triangular shape by such a method as cutting. In the case of the EL apparatus of the present invention as described above, however, the photoconductive layer 6 is formed by sintering; morerover, the luminescing current passing through the said layer flows substantially parallel to the illumination, so that the sensitivity is extremely high; and the delayed resistance drop characteristic is also excellent.

When this output EL apparatus is combined, as shown in FIG. 3, with the input EL apparatus illustrated in FIG. 1, an instantaneous luminescing of the EL layer E between the intersection of voltage-impressed electrodes illuminates one portion of the sintered photoconductive layer 6 of the output EL apparatus, whereby a delayed resistance drop effect is developed at the said portion and causes delayed luminescence in the EL layer E This effect may be illustrated graphically as in FIG. 4, wherein: graph A represents pulse voltage impressed on an intersection point; graph B represents the condition of luminescence of the layer E due to the said pulse voltage; graph C represents the condition of delayed resistance drop of the photoconductive layer 6 due to the said luminescence illumination; and graph D represents the luminescing condition of the EL layer E based on the said resistance drop. Accordingly, the net effect is that the impressing of a pulse voltage as in graph A causes luminescence as in graph D to be observed.

By using the EL'indicating apparatus of the present invention as described above, particularly in such applications as radar equipment, it is possible to obtain clear images without flickering, since it is possible to provide the apparatus with suitable afterglow or phosphorescent characteristic. Accordingly, the apparatus of the present invention has high practical worth.

While the foregoing description has related to an embodiment of the EL indicating apparatus of rectangular shape, it will be understood, of course, that other shapes may be used.

Since it is thus obvious that many changes and modifications can be made in the above-described details without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be limited to the details described herein except as set forth in the appended claims.

What is claimed is:

1. An electroluminescent indicating device which comprises in combination: an electroluminescent unit having on one surface of a layer of electroluminescent material a plurality of first parallel electrodes and on the other surface of the layer a plurality of second parallel electrodes disposed orthogonally with the said first parallel electrodes; a solid-state light amplifying apparatus consisting of heat resistant insulating posts each having on its top surface a photoconductive layer sintered in situ thereon, a first electrode on said posts and a second electrode on a side surface of said posts, said photoconductive layer being positioned between and contacting said first and second electrodes, an electroluminescent layer having a third electrode on one surface, said insulating post being adhesively bonded on said one surface of the electroluminescent layer with the second and third electrodes in electrical contact, a transparent electrode positioned on the opposite side of said electroluminescent layer and a first voltage source connected across said first electrode and said transparent electrode, a second voltage source connectable with the first and second parallel electrodes, said first voltage being applied through said photoconductive layer and said second electrode to said electro- 4 luminescent layer, said electroluminescent unit resting on the posts.

2. An electroluminescent indicating device as claimed in claim 1, wherein said insulating posts are made of ceramic material.

3. An electroluminescent indicating device which comprises in combination: an electroluminescent unit having on one surface of a layer of electroluminescent material a plurality of first parallel electrodes and on the other surface of the layer a plurality of second parallel electrodes disposed orthogonally with the said first parallel electrodes; and a solid-state light amplifying apparatus consisting of a plurality of heat-resistant, insulating posts each of which has formed thereon in situ a sintered photoconductive layer extending lengthwise along a top surface thereof, a line electrode contacting said layer along the said top surface and a plurality of discrete electrodes on the lateral side surfaces of each post contacting a side of said photoconductive layer, an electroluminescent layer having a plurality of discrete electrodes on one surface thereof, said plural heat-resistant insulating posts being mounted on said surface with the discrete electrodes of the post and conductive layer respectively in contact, said electroluminescent unit resting in the posts, a transparent electrode positioned on the opposite surface of said electroluminescent layer, a first Voltage source connected across the said line electrodes and said transparent electrode, a second voltage source connectable with the first and second parallel electrodes, said sintered photoconductive layer being thereby electrically connected to said line electrode and said discrete electrodes whereby the voltage is applied to the luminescent layer.

4. An electroluminescent indicating device as claimed in claim 3, wherein said insulating posts are made of ceramic material.

References Cited by the Examiner UNITED STATES PATENTS 2,839,690 6/58 Kazan 250-213 2,905,830 9/59 Kazan 250213 2,932,746 4/60 Jay 2S0213 2,999,165 9/61 Lieb 250213 3,059,118 10/62 Koury 2502l3 3,059,144 10/62 Bowerman 250 213 3,070,701 12/62 Wasserman 250213 FOREIGN PATENTS 851,077 10/60 Great Britain.

OTHER REFERENCES Nicoll: Light Amplifier Using Sintered Photoconductors, RCA Technical Notes No. 375, June 10, 1960.

RALPH G. NILSON, Primary Examiner.

JOHN W. HUCKERT, Examiner. 

3. AN ELECTROLUMINESCENT INDICATING DEVICE WHICH COMPRISES IN COMBINATION: AN ELECTROLUMINESCENT UNIT HAVING ON ONE SURFACE OF A LAYER OF ELECTROLUMINESCENT MATERIAL A PLURALITY OF FIRST PARALLEL ELECTRODES AND ON THE OTHER SURFACE OF THE LAYER A PLURALITY OF SECOND PARALLEL ELECTRODES DISPOSED ORTHOGONALLY WITH THE SAID FIRST PARALLEL ELECTRODES; AND A SOLID-STATE LIGHT AMPLIFYING APPARATUS CONSISTING OF A PLURALITY OF HEAT-RESISTANT, INSULATING POSTS EACH OF WHICH HAS FORMED THEREON IN SITU A SINTERED PHOTOCONDUCTIVE LAYER EXTENDING LENGTHWISE ALONG A TOP SURFACE THEREOF, A LINE ELECTRODE CONTACTING SAID LAYER ALONG THE SAID TOP SURFACE AND A PLURALITY OF DISCRETE ELECTRODES ON THE LATERAL SIDE SURFACES OF EACH POST CONTACTING A SIDE OF SAID PHOTOCONDUCTIVE LAYER, AN ELECTROLUMINESCENT LAYER HAVING A PLURALITY OF DISCRETE ELECTRODES ON ONE SURFACE THEREOF, SAID PLURAL HEAT-RESISTANT IN- 